1. Field of the Invention
The present invention relates to a tube expanding apparatus for a heat exchanger composed of a large number of radiating fins and a plurality of tubes inserted therethrough, for integrally fixing a large number of radiating fins by expanding a tube, and particularly to a heat exchanger tube expanding apparatus improved so as to prevent defects in which a fin collar buckles, placing a radiating fin and a radiating fin overlapping in a direction of lamination in close contact and shutting off an air channel.
2. Description of the Related Art
A tube expanding apparatus for a heat exchanger constituted by a large number of radiating fins and a plurality of tubes inserted through the radiating fins, for integrally fixing a plurality of radiating fins by expanding a tube inserted therethrough, conventionally has a construction such as described below, for example.
A tube expanding apparatus has a reciprocating actuator having a plurality of tube expanding mandrels inserted into a rear surface side, being disposed so as to be raisable and lowerable by means of an expanding and contracting apparatus such as a cylinder, etc. A heat exchanger in which the tubes are to be expanded has a construction in which hairpin tubes having end portions formed into a general U shape are inserted through a plurality of radiating fins, and using this tube expanding apparatus, end portions of the hairpin tubes projecting outward at one end are supported by receivers having a concave portion into which lower end portions can be inserted during tube expansion, enabling the plurality of radiating fins to be integrally fixed by pressing the tube expanding mandrels inserted into the reciprocating actuator of the tube expanding apparatus into the hairpin tubes to expand the hairpin tubes. (See Patent Literature 1, for example.)
Patent Literature 1: Japanese Patent Laid-Open No. HEI 6-254644 (Gazette, Page 2, FIG. 4)
However, in conventional tube expanding apparatuses, if the number of sheets of the radiating fins is increased or if a fin collar shape is modified, changing a relationship between a load acting on the fin collar and the amount of compression, etc., one problem has been that defects may arise in which the fin collar buckles, placing a radiating fin and a radiating fin overlapping in a direction of lamination in close contact and shutting off an air channel.